I don't often buy used. But I just washed some used trainers. I did 1.5oz of biokleen oxygen bleach on sanitize. I don't often use oxy bleach and I only recently used sanitize for the first time to kill some yeast. I figured once for "no reason" wouldn't' hurt.

Doesn't the bleach hurt the diapers? I have some prefolds and thirsties covers new to me but used I need to wash, but 1, I have a top loader HE so I don't even know how to do that... Should I just try hand washing them in a bucket or something?

Bleach every once in a while should be ok. And prefolds can take any abuse. HE should have a place for bleach I think.